Torch for applying powdered material



Oct. 8, 1968 I E. A. HAWK, SR 3,404,838

TORCH FOR APPLYING POWDERED MATERIAL Filed May 24, 1966 FIG. I.

INVENTOR Wmm 3 BY W m mmwmm.

ATTORNEYS- United States Patent 3,404,838 TORCH FOR APPLYING POWDERED MATERIAL Elwin A. Hawk, Sr., Rte. 1, East Rochester, Ohio 44625 Filed May.24, 1966, Ser. No. 552,486 9 Claims. (Cl. 239-79) ABSTRACT OF THE DISCLOSURE This torch is used for heating a metal surface and for spraying powdered metal through the flame to coat the surface with hard-facing material. Powder is aspirated into the torch from a hopper and the construction of the torch prevents backfires and explosions which in prior-art torches, blow the powder out of the hopper. Oxygen and fuel gas passages in the torch are correlated so that with gas flowing in either passage, an aspirating action is exerted on the other passage. By making the oxygen passage smaller than the fuel gas passage, the oxygen can be supplied at higher pressure and higher velocity, without unduly increasing the proportion of oxygen, and the mixed gases can be accelerated by the oxygen stream velocity to a speed higher than the rate of flame propagation through the mixture. The aspirating action on each gas passage by flow of gas in the other is effected by a nozzle which can either have the passages converge at a low angle so that they are adjacent and merged within the nozzle or discharge through the face of the nozzle at adjacent locations.

Brief description of the invention This invention relates to torches that are used for ap plying powdered material to a heated surface by discharging the powder through the flame jets of a torch.

It is an object of the invention to provide an improved torch of the character indicated, and more especially to provide a safer torch.

It is an object of the invention to prevent gases from burning within the torch. When that occurs for any extended period of time, the torch is damaged and it may be irreparably damaged. This invention prevents mixing of gas in passages within the torch so that there is less of the torch filled with a combustible mixture. According to another feature of the invention the gas passages are made small in diameter so that the gases flowing in the torch are at high velocity and the areas of cool metal around any flame that pops back into the torch is large compared to the volume of gas involved in the flame. This produces a cooling effect for extinguishing the flame.

Another object is to prevent the formation of explosive and combustible mixtures by having a construction that constitutes, in effect, parallel aspirators, one operated by the oxygen and the other by the fuel gas so that no matter which gas is turned on first, it acts to draw a partial vacuum on the powder supply passage and the other gas supply passage, and thus prevent back flow into those passages and resulting formation of combustible and explosive mixtures.

Other features of the invention relates to constructions that are economical to manufacture and assemble, and convenient to replace mixers and other standard parts when necessary to adapt the torch for use with tips in a larger or smaller range of sizes.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

Brief description of the drawings In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views;

FIGURE 1 is a vertical sectional view showing a torch constructed in accordance with this invention;

FIGURE 2 is a greatly enlarged sectional view taken on the section line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged, fragmentary, sectional view showing a modified construction for the aspirator portion of the torch shown in FIGURE 1; and

FIGURE 4 is an enlarged, fragmentary, sectional view taken on the line 44 of FIGURE 3.

Description of the preferred embodiment FIGURE 1 shows torch 10 having a body 12 with a threaded end 14 to which a tip 16 is connected by a tip nut 18. There is a shoulder 20 on the tip 16 which abuts against the downstream end of the torch body 12 to -determine the position of the tip 16 when in assembled relation with the torch body. An extension 22 of the tip fits into the torch body and reaches close to a chamber 26 located within the torch body for receiving an aspirator.

The torch includes an aspirator having two portions which include a downstream portion 30 and a nozzle portion 32. The downstream portion 30 of the aspirator has an extension 34 which fits into the upstream end of the tip extension 22 and there is an outlet passage 36 through the extension 34.

The nozzle portion 32 of the aspirator has a frustoconical, downstream end which seats against a short complementary face 40 on the downstream portion of the aspirator. Beyond this face 40, the downstream portion 30 has a taper which is complementary to that of the nozzle portion 32 and which is spaced from the nozzle portion 32 by a clearance 44.

Substantially radial powder passages 46 open through the sides of the downstream portion 30 of the aspirator into the clearance 44. At their outer ends these powder passages 46 communicate with a circumferential groove 50 in the downstream portion 30 of the aspirator.

At the upper end of the chamber which houses the aspirator, the groove 50 is located directly under a powder supply passage 54. There are valve means in this passage for controlling the flow of powder. Different kinds of Valve means can be used. The one illustrated in the drawing is a flexible tube 56 which is pinched by a plunger 58 to shut oif the flow of powder from a supply hopper 60 which screws into the upper end of the body 12. The plunger 58 is connected with a bell crank 62 attached to the torch body by a pivot 64 and having a handle portion 66 which is held in an upward position by a compression spring 68. Compression spring 68 keeps the flexible tube 56 closed and shuts off flow of powder.

The handle 66 extends to a handle portion 72 of the torch 10 so that this handle 66 can be operated by a person holding the torch 10 whenever a supply of powder is desired. Powder drops from the supply hopper 60 into the upper end of the powder passage 54 and is held against further flow by the pinched section of the flexible tube 56 unless the handle 66 is depressed.

When the handle 66 is depressed so as to pull the plunger 58 to the right in FIGURE 1, powder can flow by gravity through the powder supply passage 54 and into the groove 50 and through any passage 46 which happens to be near the top of the torch body. However, gravity feed is only relied upon to bring the powder down into the aspirator, and further feed of powder is effected by the aspirator itself.

There are two supply passages in the aspirator nozzle portion 32. There is a center passage 76 for oxygen and a side passage 78 for fuel gas. In the construction shown in FIGURE 1 the fuel gas passage 78 enters the oxygen passage on a slope and in such a direction that the passages 76 and 78 converge as they approach the discharge end of the nozzle portion 32.

The nozzle portion 32 discharges into the outlet passage 36 which is of larger diameter than the oxygen passage 76 or the fuel gas passage 78. There is also some clearance between the end of the nozzle portion 32 and the beginning of the uniform diameter outlet passage 36, and the expansion of the gas stream from the nozzle portion 32 into this enlarged space produces an aspirator action that creates a partial vacuum in the clearance 44 so that powder is drawn through the passages 46 and discharged, with the gases from the nozzle portion 32, into the outlet passage 36. This outlet passage 36 serves as a mixing chamber for the torch.

Because of the way in which the passages 76 and 78 are brought together, it will be evident that gas flowing in either of these passages 76 or 78, when there is no gas flow in the other passage, will exert an aspirator action on the other passage and create a partial vacuum on the other passage. The effect is that the flow of oxygen, when there is no supply of fuel gas, creates a suction on the fuel gas supply passage 78 and prevents oxygen from travelling back into the fuel gas line. Similarly, the flow of gas through the fuel gas line 78, when there is no gas supplied to the oxygen supply line 76, exerts a partial vacuum on the oxygen supply line and prevents fuel gas from travelling back into the oxygen supply line. In this way the building up of mixed gases in the torch upstream from the nozzle portion 32 is avoided regardless of which of the gases is turned on first when the torch is started up, and regardless of the fact that the gas supplied through the different passages 76 and 78 is usually at different pressures.

When gas is flowing in both of the passages 76 and 78, there is still the aspirator effect, but the presence of gas in the other passage prevents the reduction of pressure to a partial vacuum. It will also be apparent that the operation of the aspirator to draw powder can be effected by either the oxygen or the fuel gas supply, but ordinarily the valve for powder is not opened until the torch has been lighted and both gases are turned on so as to obtain maximum heat for raising the temperature of the workpiece to an advantageous degree for receiving the powder.

In accordance with one feature of the invention, the gas passages are kept small enough to insure high velocity flow, and they are of different cross sections depending upon the pressure of the gas used in the respective torches. For example, if the oxygen is to be supplied to the passage 76 at a pressure of 24 pounds per square inch and the acetylene is to be supplied to the passage 78 at a pressure of 12 pounds per square inch, then the cross section of the oxygen passage 76 is made one-half as great as the cross section of the acetylene passage 78. This results in equal quantities of acetylene and oxygen being supplied to the mixer with the same flow velocity in the passages 76 and 78.

If the oxygen is to be supplied at a pressure three times as great as that of the acetylene, then the cross section of the acetylene passage is made three times as great as that of the oxygen passage. Thus the ratio of the cross section of the oxygen and acetylene passages to one another are inversely proportional to the oxygen and acetylene pressure ratio of the gas pressures with which the torch is intended to be used. In the pressure constructions of the torch, the cross section of the oxygen and acetylene passages are proportioned for acetylene to oxygen pressures ranging from 1/2 to 1/ 10.

Preferably the outlet passage 36 has a cross section approximately equal to the sum of the cross section of the oxygen and fuel gas passages 76 and 78, respectively, though the outlet passage through which the gas flows increases substantially in cross section after the mixed gases reach the interior of the tip 16. The cross section of the outlet passage 36 should be maintained for a distance equal to several times the diameter of the outlet passage 36 and it is then desirable to have the cross section increase abruptly.

The cross section of the gas passages 76 and 78 is kept small so that a substantial velocity is obtained in the aspirator. It is desirable to maintain a vacuum of at least four inches of mercury at the powder passages 46. It is also desirable to maintain a high velocity of gas flow so that flames cannot burn back through the mixer. The velocity of the mixed gases, therefore, should be above the rate of flame propagation when the torch is operated normally.

In the event of an obstruction which prevents escape of gas from the tip, the rate of gas flow decreases and the torch can backfire, but it does not continue to burn inside because with the gas fiow blocked, new gas cannot enter the torch to support combustion. The higher oxygen pressure does not cause oxygen to flow back into the acetylene passage to any extent because the gas in the acetylene passage cannot be pushed back through the pressure regulators from which the gas is supplied.

For any particular size of gas passages, the tip 16 must be within a range of cross section which prevents backfires during noral operation and at the same time provide ample vacuum at the aspirator. If the passage through the tip 16 is too large, the velocity of the gas flow will be less than the rate of flame propagation and the tip will backfire. If the cross section of the gas passage through the tip is too small, the gas flow through the aspirator is partially blocked and the gas velocity will not be sufficient to maintain the desired vacuum of four inches of mercury.

The chamber which holds the aspirator and the torch body 12 terminates in a threaded counterbore 82; and the handle portion 72 of the torch has a threaded plug 84 at one end which screws into the threaded counterbore 82 to clamp the nozzle portion 32 of the aspirator against the downstream portion 30, and to clamp the latter against a shoulder 86 in the torch body 12. There is preferably a packing ring at the shoulder to prevent leakage of gas and there is a similar packing ring 88 between the extension 22 of the tip and the front face of the downstream end of the aspirator.

There are gas passages through the handle 72 and plug 84 including a passage 92 for oxygen and a passage 94 for fuel gas. The oxygen passage 92 communicates with an annular groove 96 in an end wall of the nozzle portion 32 of the aspirator; and the fuel gas passage 94 communi cates with an annular groove 98 in the end face of the nozzle portion 32 of the aspirator. The gas suppl passages 76 and 78 communicate with the same annular grooves 96 and 98, respectively, so that regardless of the angular position of the nozzle portion 32 of the aspirator, or the plug 84 in the body of the torch, the oxygen supply passage 92 is always in communication with the passage 76, and the fuel gas supply passage 94 is always in communication with the passage 78.

FIGURE 1 shows knobs 100 and 101 for operating valves which command the gas supply passages 92 and 94 respectively; and there are regulators 104 in series with the valves 100 and 101 for controlling the pressure at which the gases are supplied to the torch.

A sealing ring 88 is located in an annular groove in the end face of the nozzle portion 32 of the aspirator between the annular grooves 96 and 98 for preventing leakage of gas between the different gas supply passages. It will be evident that this groove could be in the plug 84 instead of in the nozzle portion of the aspirator, and the same is true of the annular grooves 96 and 98.

FIGURE 3 shows a modified construction for the nozzle portion of the aspirator. The parts in FIGURE 3 which correspond to those in FIGURE 1 are indicated by the same reference characters with a prime appended. The only difference in construction is that a nozzle portion 32' of the aspirator has an oxygen supply passage 76' and a fuel gas supply passage 78 which do not come together in the nozzle portion. Instead, these gas supply passages 76 and 78' extend side by side and generall parallel to one another until they reach the outlet end of the nozzle portion 32' and discharge into the passage 36'. The operation is substantially the same as in FIGURE 1 in that the discharge ends of both of the passages 76 and 78 are sufliciently close together so that when there is no gas supplied to one of these passages, gas flow from the other passage exerts an aspirator action as described in connection with FIGURE 1. The construction shown in FIG- URE 3 can be considered as parallel aspirators and the condition shown in FIGURE 2 can be considered as series aspirators.

The preferred embodiments of the invention have been illustrated and described, but changes and modifications can be made and some features can be used in different combinations without departing from the invention as defined in the claims.

What is claimed is:

1. A powder spray torch having a chamber therein, a powder supply passage through which powder enters the chamber for discharge through an outlet passage to a flame jet orifice of a tip of the torch, an aspirator in the chamber in position to draw powder into the torch through said powder supply passage, the aspirator including a nozzle that discharges gas into saidoutlet passage, an oxygen supply passage in the torch, a fuel gas supply passage in the torch of larger cross section than the oxygen supply passage, separate valves controlling the supply of oxygen and fuel gas, both the oxygen and fuel gas supply passages extending through the nozzle, and having end portions that discharge adjacent to one another and in directions that make the oxygen flowing from the oxygen supply passage exert an aspirator action on the fuel gas passage whereby the oxygen and fuel gas can be supplied to the nozzle at different pressures and excess of oxygen pressure can be used to increase the velocity of the fuel gas.

2. The powder spray torch described in claim 1 characterized by one of the supply passages opening into the other supply passage upstream from the discharge end of the nozzle and along a converging course to said other supply passage in the direction of gas flow so as to exert an aspirator action on said other supply passage to create a reduced pressure therein that prevents back flow of gases into said other supply passage.

3. The powder spray torch described in claim 2 characterized by the fuel gas supply passage being the one that open-s into the other supply passage and being at an angle to draw a partial vacuum on the oxygen supply passage upstream from the location where the fuel gas supply passage opens into said oxygen supply passage.

4. The powder spray torch described in claim 1 characterized by the nozzle having two discharge orifices therein located side by side on the outlet end of the nozzle, one of said discharge orifices being a termination of the fuel gas supply passage.

5. The powder spray torch described in claim 4 characterized by a mixing chamber of substantial length in the direction of gas flow at the downstream end of the 6 aspirator and into which both of the discharge orifices of the nozzle are directed.

6. The powder spray torch described in claim 1 characterized by a part of the length of the outlet passage constituting a mixing chamber and having a cross section approximately equal to the sum of the cross sections of the oxygen and fuel gas supply passages whereby the gases remain at high velocity as they travel through the mixing chamber, and the outlet passage increasing in cross section downstream from said mixing chamber.

7. The powder spray torch described in claim 1 characterized by the oxygen and fuel gas supply passages being of different cross sectional areas, the ratio of the cross section of the oxygen passage to the cross section of the fuel gas passage being inversely proportional to the ratio of the pressures at which the gases are intended to be supplied to the passages, and the mixing chamber to which gases are supplied from both the oxygen and the fuel gas passages being of a cross section equal to the combined cross sections of the oxygen and fuel gas passages, the ratio of the cross section of the oxygen passage to that of the fuel gas passage being between 1/2 and 1/10.

8. The powder spray torch described in claim 1 characterized by the aspirator having a downstream portion with a tapered end face confronting the nozzle, said nozzle having a tapered end face confronting said downstream portion, abutment surfaces on the different portions of the aspirator holding them in position with most of the area of at least one of the tapered faces spaced from the other of the tapered faces, a plug behind the nozzle and through which the oxygen and fuel gas supply passages extend on their way to the nozzle, said plug holding the different parts of the aspirator in assembled relation with one another.

9. The powder spray torch described in claim 8 characterized by a shoulder in the chamber and against which the downstream end of the downstream portion of the aspirator abuts, concentric annular channels in the upstream end of the nozzle portion of the aspirator and into which the oxygen and fuel gas passages in the nozzle open, the oxygen and fuel gas supply passages in the plug communicating with the respective channels in the nozzle portion of the aspirator, screw threads holding the plug against the nozzle portion and clamping the aspirator against the shoulder, sealing means in the torch preventing flow of gas through clearances other than the channels and passages, and valve means upstream from the plug commanding the oxygen and fuel gas supply I passages.

References Cited UNITED STATES PATENTS 2,786,779 3/1957 Long et al. 239- X 3,190,560 6/1965 Schilling et al 239-85 FOREIGN PATENTS 59,478 3/1919 Sweden.

M. HENSON WOOD, JR., Primary Examiner. M. Y. MAR, Assistant Examiner. 

